This application claims foreign priority under 35 USC 119 from Japanese Applications 11-249888 filed Sep. 3, 1999 and 11-312239 filed Nov. 2, 1999.
The present invention relates to a composition or compound each having a tertiary amine structure and having chelate effects and biodegradability, to a process for producing said composition or compound, and to a chelating agent comprising said composition or compound. More particularly, the invention relates to an amino acid derivative composition and a process for producing an amino acid derivative. The present invention also relates to an L-aspartic acid derivative, a process for producing an L-aspartic acid derivative, an L-aspartic acid derivative composition, a process for producing an L-aspartic acid derivative composition, and a chelating agent. The invention further relates to a process for producing N-bishydroxyalkyl-amino acids and a process for producing N-bishydroxyethylaspartic acids.
Chelating agents can sequester metal ions by forming 2 or more coordinate bonds and therefore are used for eliminating harmful influences exerted by the presence of metal ions in various fields, such as in the fields of detergents, textiles, paper and pulp, metal surface treatment and photography, among others, and they are now indispensable to chemical industries and daily life.
In the field of detergents, for instance, chelating agents are used to remove metal ions, such as calcium and magnesium ions, in hard water for rendering the water usable for the intended purpose and, in the field of textiles, paper and pulp, for instance, they are used to prevent hydrogen peroxide and like bleaching agents from being decomposed in the presence of metal ions. As typical chelating agents, there may be mentioned, among others, ethylenediaminetetraacetic acid (EDTA) and the like, which are inexpensive and are high in chelating power.
These chelating agents are disposed of in a state contained in household waste water and industrial waste. Therefore, if they are hardly biodegradable, they may have unfavorable influences on the environment and ecological system. Generally, the term xe2x80x9cbiodegradabilityxe2x80x9d means that a substance can be decomposed spontaneously by microorganisms or products thereof in nature and the decomposition products do not have harmful influences on the environment and ecosystem any longer.
In recent years, the regulations against environmental pollution by chemical substances have become more and more strict. The current situation is such that the use of those chelating agents which are lacking in biodegradability is hesitated. Therefore, various investigations are in progress in search of chelating agents having improved biodegradability.
Japanese Kokai Publication Hei-08-208569 discloses the technology of using a diethanolamine derivative as a chelating agent. This diethanolamine derivative is produced by reacting diethanolamine with maleic acid and/or a salt thereof in the presence of an alkaline earth metal. Its carboxyl groups occurring around the nitrogen atom and the ether group-derived oxygen atom, which serve as central atoms, effectively produce its chelating activity. Furthermore, the derivative has such a high level of biodegradability that none of the conventional chelating agents can be equal to it in that respect. However, there is still room for improvement in chelating effect and biodegradability.
Japanese Kohyo Publication Hei-10-502632 discloses a process for producing salts of [S,S]-ethylenediamine-N,Nxe2x80x2-disuccinic acid (ss-EDDS) which comprises the step of reacting L-aspartic acid with a 1,2-dihaloethane in a basic aqueous solution in which the amount of 1,2-dihaloethane is stoichiometrically insufficient throughout the reaction period so that less than 60 mole percent of the initial charge of L-aspartic acid can react. It has been found that the sodium salt of the above ss-EDDS is useful as a biodegradable chelating agent. However, in view of the chemical structure of ss-EDDS, there is still room for technical improvement for producing the chelating activity more efficiently or increasing the biodegradability.
Laid-open International Patent Specification WO 97/45396 discloses an N-bis- or N-tris[(1,2-dicarboxy-ethoxy)-ethyl]-amine derivative as a biodegradable chelating agent. This amine derivative can be produced by reacting di- or triethanolamine with maleic acid in the presence of an alkali metal or alkaline earth metal salt, using a lanthanide compound, a lanthanide compound mixture or an alkaline earth metal compound as a catalyst. However, such compounds have two or more asymmetric carbon atoms but their configurations have not been specified as yet. It is thus difficult to expect that they are surely biodegradable.
Japanese Kokai Publication Hei-06-59422 discloses a treatment composition for silver halide-containing photosensitive materials which contains an N-bishydroxyethylaspartic acid salt or the like as a chelating agent. Since the N-bishydroxyethylaspartic acid salt or the like has a chelating activity, this treatment composition is suited for rapid treatment with efficient desilverization. Since said salt or the like has biodegradability, the possibility of environmental pollution by the composition is much less. Thus, N-bishydroxyethylaspartic acids are themselves useful as chelating compounds. In recent years, they have been regarded as promising also as intermediates for the production of compounds having the basic skeleton of aspartic acid within the molecule.
A process for producing these N-bishydroxyethylaspartic acids is disclosed in Problemy Khimii Kompleksonov (1985) (in Russian), pp. 108-115. This process comprises the step of esterifying aspartic acid in a methanol/hydrochloric acid solution to give dimethyl aspartate, the step of causing ethylene oxide to add to dimethyl aspartate and the subsequent step of hydrolyzing the addition product with sodium hydroxide or the like. This process, however, involves a number of steps, hence byproduct formation is highly possible. Further, the production cost is high and it is difficult to expect improvements in yield.
It is an object of the present invention, which has been made in view of the above-mentioned state of the art, to provide a composition or compound having sufficient chelating activity and remarkably high biodegradability, a process for producing said composition or compound, and a chelating agent comprising said composition or compound. Another object of the present invention is to provide a simplified process for producing N-bishydroxyalkyl-amino acids having chelating activity and biodegradability in improved yields while reducing the possibility of byproduct formation.
The present invention provides an amino acid derivative composition which comprises two or more kinds of amino acid derivatives represented by the general formula (1): 
wherein R""s are the same or different and each represents a hydrogen atom or an alkyl group containing 1 to 18 carbon atoms; L1 represents xe2x80x94M1xe2x80x94X or xe2x80x94CHXxe2x80x94M2xe2x80x94X; L2 represents xe2x80x94CH2xe2x80x94M3xe2x80x94X or xe2x80x94CHXxe2x80x94M4xe2x80x94X; M1, M2, M3 and M4 are the same or different and each represents a straight or branched alkylene group containing 1 to 6 carbon atoms; X represents COOM; M""s are the same or different and each represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom or an ammonium group; m represents an integer of 1 or 2 and n represents an integer of 0 or 1 on the condition that m+n is equal to 2.
The present invention also provides a process for producing the amino acid derivative represented by the above general formula (1) (wherein R represents a hydrogen atom or an alkyl group containing 1 to 18 carbon atoms; L1, L2, M1, M2, M3, M4, X, m and n are defined as above)
which comprises the steps of:
causing an alkylene oxide to add to an amino acid
and reacting the amino acid-alkylene oxide adduct with an unsaturated carboxylic acid in the presence of a rare earth-based catalyst.
The present invention further provides a chelating agent which comprises the amino acid derivative composition.
The invention also provides an L-aspartic acid derivative represented by the general formula (2): 
wherein X, m and are as defined above and * indicates that the asymmetric carbon atom carrying this symbol is in S configuration.
The invention further provides a process for producing the above L-aspartic acid derivative
which comprises the steps of:
causing ethylene oxide to add to L-aspartic acid
and reacting the resulting L-aspartic acid-ethylene oxide adduct with maleic acid in the presence of a rare earth-based catalyst.
The invention still further provides a chelating agent which comprises the above L-aspartic acid derivative.
The invention also provides an L-aspartic acid derivative composition
which comprises an L-aspartic acid derivative (A) and an L-aspartic acid derivative (B),
said derivative (A) being represented by the general formula (3): 
wherein X is as defined above and * indicates that the asymmetric carbon atom carrying this symbol is in S configuration,
and said derivative (B) being represented by the general formula (4): 
wherein X is as defined above and indicates that the asymmetric carbon atom carrying this symbol is in S configuration,
wherein, in said L-aspartic acid derivative composition, the occurrence ratio (mole ratio) between said derivative (A) and said derivative (B) is in the range of 1:99 to 99:1.
The present invention further provides a process for producing the above L-aspartic acid derivative composition
which comprises the steps of:
causing ethylene oxide to add to L-aspartic acid
and reacting the resulting L-aspartic acid-ethylene oxide adduct with maleic acid in the presence of a rare earth-based catalyst.
The invention still further provides a chelating agent
which comprises the above L-aspartic acid derivative composition.
The invention further provides a process for producing N-bishydroxyalkyl-amino acids represented by the general formula (5): 
wherein R represents a hydrogen atom or an alkyl group containing 1 to 18 carbon atoms; L1, M1, M2 and X are as defined above,
which comprises the step of causing an alkylene oxide to add to an amino acid salt in an aqueous solution.
Finally, the invention provides a process for producing N-bishydroxyethylaspartic acids represented by the general formula (6): 
wherein X is as defined above,
which comprises the step of causing ethylene oxide to add to an aspartic acid salt in an aqueous solution.